From c2da074b7c50264817cc4a8647b348dd6a7780d4 Mon Sep 17 00:00:00 2001
From: Thibaud <thibaud.gasser@gmx.com>
Date: Wed, 27 May 2026 22:54:26 +0200
Subject: [PATCH] 2O15 day 3, 4, and 6 part 1

---
 adventofcode/2015/day3/day3.py | 52 +++++++++++++++++++++++++++++++
 adventofcode/2015/day4/day4.py | 56 ++++++++++++++++++++++++++++++++++
 adventofcode/2015/day6/day6.py | 36 ++++++++++++++++++++++
 3 files changed, 144 insertions(+)
 create mode 100644 adventofcode/2015/day3/day3.py
 create mode 100644 adventofcode/2015/day4/day4.py
 create mode 100644 adventofcode/2015/day6/day6.py

diff --git a/adventofcode/2015/day3/day3.py b/adventofcode/2015/day3/day3.py
new file mode 100644
index 0000000..e8d4514
--- /dev/null
+++ b/adventofcode/2015/day3/day3.py
@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+import fileinput
+from itertools import zip_longest
+
+
+def grouper(n, iterable):
+    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
+    args = [iter(iterable)] * n
+    return zip_longest(*args)
+
+
+def move(c, x, y):
+    if c == "^":
+        y += 1
+    elif c == ">":
+        x += 1
+    elif c == "v":
+        y -= 1
+    elif c == "<":
+        x -= 1
+    return x, y
+
+
+def part1(inp):
+    x, y = 0, 0
+    visited = {(x, y)}
+    for c in inp:
+        x, y = move(c, x, y)
+        visited.add((x, y))
+    print("Part 1: ", len(visited))
+
+
+def part2(inp):
+    x1, y1 = 0, 0
+    x2, y2 = 0, 0
+    visited = {(x1, y1)}
+    for move1, move2 in grouper(2, inp):
+        x1, y1 = move(move1, x1, y1)
+        x2, y2 = move(move2, x2, y2)
+        visited.add((x1, y1))
+        visited.add((x2, y2))
+    print("Part 2: ", len(visited))
+
+
+def main(inp):
+    part1(inp)
+    part2(inp)
+
+
+if __name__ == "__main__":
+    inp = next(x.rstrip() for x in fileinput.input())
+    main(inp)
diff --git a/adventofcode/2015/day4/day4.py b/adventofcode/2015/day4/day4.py
new file mode 100644
index 0000000..f15a426
--- /dev/null
+++ b/adventofcode/2015/day4/day4.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+import sys
+from hashlib import md5
+from multiprocessing import Process, Value
+
+
+def solve(seed):
+    needle = "0" * 5
+    for i in range(900_000):
+        hash = md5(seed + str(i).encode()).hexdigest()
+        if hash.startswith(needle):
+            # print(hash)
+            return i
+    assert False, "No solution found"
+
+
+def worker(seed, start, step, stop_token, result):
+    i = start
+    while not stop_token.value:
+        d = md5(seed + str(i).encode()).digest()
+        if d[0] == 0 and d[1] == 0 and d[2] == 0:
+            stop_token.value = 1
+            result.value = i  # Store the result
+            return
+        i += step
+
+
+def solve_parallel(seed):
+    stop_token = Value("b", 0, lock=False)
+    result = Value("i", -1)  # Default: -1 (no result yet)
+    workers = []
+    num_workers = 8
+    for w in range(num_workers):
+        p = Process(target=worker, args=(seed, w, num_workers, stop_token, result))
+        p.start()
+        workers.append(p)
+
+    for p in workers:
+        p.join()
+
+    # Print the result
+    if result.value != -1:
+        return result.value
+    else:
+        assert False, "No solution found"
+
+
+def main(inp):
+    print("Part 1: ", solve(inp))
+    print("Part 2: ", solve_parallel(inp))
+
+
+if __name__ == "__main__":
+    filename = sys.argv[1] if len(sys.argv) > 1 else "file not found"
+    with open(filename, "rb") as f:
+        main(f.readline().rstrip())
diff --git a/adventofcode/2015/day6/day6.py b/adventofcode/2015/day6/day6.py
new file mode 100644
index 0000000..8aef340
--- /dev/null
+++ b/adventofcode/2015/day6/day6.py
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+import fileinput
+import re
+
+
+def part1(inp):
+    """
+    Part 1: simple brute force solution. Use a 1D array to represent the grid.
+    Use sice operations whenever possible because they are faster than iterating.
+    """
+    grid = [False] * 1000 * 1000
+    for line in inp:
+        x1, y1, x2, y2 = map(int, re.findall(r"(\d+)", line))
+        x1, x2 = min(x1, x2), max(x1, x2)
+        y1, y2 = min(y1, y2), max(y1, y2)
+        for y in range(y1, y2 + 1):
+            start = y * 1000 + x1
+            end = y * 1000 + x2 + 1
+            # assigning to the slice is faster than iterating
+            if line.startswith("turn on"):
+                grid[start:end] = [True] * (end - start)
+            elif line.startswith("turn off"):
+                grid[start:end] = [False] * (end - start)
+            elif line.startswith("toggle"):
+                for i in range(start, end):
+                    grid[i] = not grid[i]
+    return sum(grid)
+
+
+def main(inp):
+    print("Part 1: ", part1(inp))
+
+
+if __name__ == "__main__":
+    lines = [x.rstrip() for x in fileinput.input()]
+    main(lines)